Multi-conduit riser with a flexible joint

ABSTRACT

A multi-conduit riser, primarily for use in underwater installation, has its larger center core conduit connected to a fixed structure on the ocean floor by a ball and socket assembly and has each of its smaller conduits that are disposed around the center core conduit forming a 360* loop near the ocean floor before communication with the fixed structure to provide a pinned connection.

United States Patent Morgan I [54] MULTI-CONDUIT RISER WITH A FLEXIBLE JOINT [72] Inventor: George W. Morgan, Anaheim, Calif.

[73] Assignee: Subsea Equipment Associates Limited, Hamilton, Bermuda 221 Filed: Nov. 23, 1970 21 Appl.No.:91,749

[52] US. Cl. .;....285/137 R, 166/.5, 285/261 [51] Int. Cl ..F16l 39/00 [58] Field of Search ..285/137 R, 261, 223; 166/.5,

[56] References Cited UNITED STATES PATENTS 6 I965 Haeber ..166/.6 4/1965 Kofahl ..166/.5

[ 1 Oct. 31, 1972 3,315,741 4/1967 Triplett ..175/7 FOREIGN PATENTS OR APPLICATIONS 292,690 7/1965 Netherlands ..166/.5

1,525,842 12/1968 Germany ..285/137R Primary Examiner-Dave W. Arola AttorneyAllan Rothenberg, Richard F. Carr and Richard L. Gausewitz [57] ABSTRACT A multi-conduit riser, primarily for use in underwater installation, has its larger center core conduit connected to a fixed structure on the ocean floor by a ball and socket assembly and has each of its smaller conduits that are disposed around the center core conduit forming a 360 loop near the ocean floor before communication with the fixed structure to provide a pinned connection.

10 Claims, 3 Drawing Figures Pmmmncmw 3.101.551 su n1ur2 INVENTOR. GEORGE W. MORGAN A T TORNE Y PATENIEBncIar' y 3.701.551

,SHEEIIZUFIVZ INVENTOR. GEORGE W. MORGAN ATTORNEY MULTI-CONDUIT RISER WITH A FLEIIIBLE JOINT FIELD OF INVENTION This invention relates to a multi-conduit riser and, more particularly, to a multi-conduit riser having a flexible connection at the ocean floor.

BACKGROUND OF THE INVENTION The point of connection of multi-conduit risers to the ocean bottom is subjected to the greatest bending moment due to the shifting of ocean currents and the floating vessel. The prior-art suggests that the riser be made sufficiently rigid to withstand these bending stresses making it bulky and massive. A pivotal connection may 7 be provided that bends with the bending stresses. Up to now pivotal connections that would perform this function were complicated and expensive.

OBJECTS OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing a flexible multi-conduit pipeline used as a riser connecting an undersea tank to a moored ship;

FIG. 2 is an enlarged elevation of the lower portion of the riser of FIG. 1 just above the fixed structure showing the details of the preferred embodiment of the pivotal, flexible joint; and

FIG. 3 is a sectional view taken on line 3-3 in FIG. 2 in the direction of the arrows.

OPERATING DESCRIPTION OF THE DRAWINGS Referring to the drawing, and to FIG. 1 in particular, a typical system utilizing a multi-conduit pipeline is shown. The pipeline is used as a riser 11 that transfers material, fluids, and power from an undersea station 12 on the ocean floor 13 to a floating ship 14 at the ocean surface 15, or transfers them from the ship to the station. The depth of the water is, for example, 2,000 feet and therefore the riser is required to support a relatively large deadweight and should be strong in tension. The ship is moored and held in place by suitable mooring lines 16 of which two are shown. Since the sea has tides. current and surface winds and since the mooring lines 16 stretch, the ship 14 moves relatively large distances from a point directly over the station 12 and the riser bows due to its weight and ocean currents causing further bending therein. Therefore, the riser 11 needs to have a relatively large degree of flexibility at its connection to the structure 12. A one pipe riser can be readily connected to the station 12 and have sufficient flexibility. A multi-conduit riser would be more difficult to connect to a structure. Therefore, my invention provides means to make the connection and to decrease the stiffness.

Referring to FIGS. 2 and 3, novel means are shown to decrease the stiffness or increase the flexibility. For simplicity, the riser 11 is shown with a center pipe 21 and only four outer pipes 22, 23, 24, 25 (more clearly shown in FIG. 3). If needed, the outer pipes may be more or less than four in number without departing from the teachings of this invention. The center pipe 21 has two pipe sections 31 and 32 joined together by a standard ball and socket assembly 35. The lower section 32 is rigidly attached to station 12 by standard means not shown. The ball and socket assembly 35 provides the necessary flexibility to pipe 21. The ball and socket assembly or joint 35 is common in the art and therefore the construction details are not shown. To provide flexibility, to the four outer pipes 22-25, each pipe is provided with a 360 loop 41 with a sufficient diameter to allow the pipes to bend the required amount. Each peripheral or outer pipe extends axially across and along said core pipe above and below the ball and socket assembly 35. The lower ends of the four pipes 22-25 are fixed to the station 12 in a standard manner not shown.

As the laws of physics explain this phenomenon, the degree of bending stresses in the pipes is inversely related to the loop diameter so that the yield point of the material is not reached. Each of the four pipes 22-25 has a loop 41 located opposite the ball and socket joint 35 or, in other words, in axial alignment therewith as shown, thereby providing the maximum amount of flexibility to the riser 1 1.

With the present disclosure in view, modification thereof would appear to those skilled in the art. Accordingly, the invention is not limited to the illustrated embodiment but includes all such modifications and variations within the scope of the invention as defined in the appended claims.

What is claimed is:

1. A pipeline for connection to a fixed station comprising:

a core pipe,

a plurality of conduits disposed around said core pipe with said conduits having 360 loops formed therein and disposed substantially within the plane of said core pipe and radiating therefrom, and said pipe and conduits being coupled to said station.

2. The pipeline of claim 1 wherein:

said core pipe is made of at least two sections; and

means are provided to join said sections together end to end to provide flexibility, passageway through the sections, and tension strength to the core pipe.

3. The pipeline of claim 2 wherein:

said loops are disposed in axial alignment with said means for joining.

4. The pipeline of claim 2 wherein:

said means is a ball and socket assembly.

5. The pipeline of claim 4 wherein:

said loops are disposed in axial alignment with said ball and socket assembly.

6. The pipeline of claim 5 wherein:

said ball and socket assembly is disposed adjacent said station.

' 7. A pipeline for connection between a fixed subaqueous station and a surface station comprising:

3 v 4 a core pipe extending upwardly from said subaquebending of said loops, each loop having a curvaous station toward said Surface at ture sufficiently large to avoid excessive bending P means fluibly connecting Said core P p to Said stresses therein when said core pipe flexes about subaqueous station, a plurality of peripheral conid pivot means duits connecied to Said SubaqueOus station and 5 8. The pipeline of claim 7 wherein each loop extends disposed f s aid core pipe and extending for 360 and has its center in axial alignment with said ally across said pivot means and along said core pivot means pipe above and below said pivot means said 9. The pipeline of claim 7 wherein each loop is quits each being bent P a loop that is posi' formed in a plane containing the axis of said core pipe. Q almigslde of Sand means whereby as l0 10 The pipeline of claim 9 wherein each loop is a said core pipe flexes about said pivot means, como single 360 bend.

pressive and tensile forces that are exerted upon said peripheralconduits by such flexing cause 

1. A pipeline for connection to a fixed station comprising: a core pipe, a plurality of conduits disposed around said core pipe with said conduits having 360* loops formed therein and disposed substantially within the plane of said core pipe and radiating therefrom, and said pipe and conduits being coupled to said station.
 2. The pipeline of claim 1 wherein: said core pipe is made of at least two sections; and means are provided to join said sections together end to end to provide flexibility, passageway through the sections, and tension strength to the core pipe.
 3. The pipeline of claim 2 wherein: said loops are disposed in axial alignment with said means for joining.
 4. The pipeline of claim 2 wherein: said means is a ball and socket assembly.
 5. The pipeline of claim 4 wherein: said loops are disposed in axial alignment with said ball and socket assembly.
 6. The pipeline of claim 5 wherein: said ball and socket assembly is disposed adjacent said station.
 7. A pipeline for connection between a fixed subaqueous station and a surface station comprising: a core pipe extending upwardly from said subaqueous station toward said surface station, pivot means flexibly connecting said core pipe to said subaqueous station, a plurality of peripheral conduits connected to said subaqueous station and disposed around said core pipe and extending axially across said pivot means and along said core pipe above and below said pivot means, said conduits each being bent to form a loop that is positioned alongside of said pivot means, whereby as said core pipe flexes about said pivot means, compressive and tensile forces that are exerted upon said peripheral conduits by such flexing cause bending of said loops, each loop having a curvature sufficiently large to avoid excessive bending stresses therein when said core pipe flexes about said pivot means.
 8. The pipeline of claim 7 wherein each loop extends for 360* and has its center in axial alignment with said pivot means.
 9. The pipeline of claim 7 wherein each loop is formed in a plane containing the axis of said core pipe.
 10. The pipeline of claim 9 wherein each loop is a single 360* bend. 